Alignment and registration targets for charged particle beam substrate patterning and inspection

ABSTRACT

The present application discloses methods, systems and devices for using charged particle beam tools to pattern and inspect a substrate. The inventors have discovered that it is highly advantageous to use patterns generated using the Hadamard transform as alignment and registration marks (Hadamard targets) for multiple-column charged particle beam substrate processing and inspection tools. Hadamard targets can be written to a substrate using charged particle beams performing, for example, resist-based lithography or resist-less direct processing. High-order Hadamard targets can also be patterned and imaged to obtain superior column performance metrics for applications such as super-rapid beam calibration DOE, column matching, and column performance tracking. Hadamard target blocks can be written highly locally to electrically functional pattern portions, or integrated into said pattern portions, thereby enabling re-registration local and contemporaneous to writing and improving beam targeting accuracy following re-registration. Superior alignment and registration, and column parameter optimization, allow significant yield gains.

CROSS-REFERENCE

This application is a continuation-in-part of, and claims priority from,U.S. patent application Ser. No. 14/522,563, filed Oct. 23, 2014; whichis a non-provisional of, and claims priority from, U.S. Provisional App.No. 61/975,721, filed Apr. 4, 2014, and U.S. Provisional App. No.61/910,021, filed Nov. 27, 2013; all of which are hereby incorporated byreference.

BACKGROUND

The present application relates to systems, devices and methods forsubstrate patterning and inspection using charged particle beams; andmore particularly to alignment and registration of charged particle beamcolumns with respect to a semiconductor wafer or other substrate, and/orto previously written patterns thereon.

Note that the points discussed below may reflect the hindsight gainedfrom the disclosed inventions, and are not necessarily admitted to beprior art.

FIG. 2A shows an example of a wafer 200 being scanned by multipleelectron beams 204 (e-beams) emitted by respective beam columns 206(e-beam columns, see FIG. 2B). A patterned or unpatterned wafer 200 (orother substrate) is independently and simultaneously scanned by multiplecolumns 206 to either write or inspect the wafer 200. Columns 206 can beseparately controlled—e.g., with different deflections and differentblanking timings. (One of ordinary skill in the arts of charged particlebeam substrate processing will recognize that a wide variety of othercontrol options are available per-column.) When writing a wafer 200 (orother substrate), the columns 206 emit electron beams 204 at a powerlevel sufficient to change certain properties of a resist layer coatedon the substrate so that after the resist is developed (in ways similarto developing a photographic film), etch steps can take place. Wheninspecting a wafer 200, the columns 206 emit electron beams 204(generally at a lower power level than when writing) and detect an imageof the substrate surface caused by the resulting scattered electrons.Individual columns 206 are able to target a portion 202 of the substratesurface with their respectively emitted beams 204.

In preferred embodiments, the array of electron beam columns 206 isstationary, the stage holding the wafer 200 moves back and forth, andthe electron beam column 206 moves the beam 204 across the wafer 200 towrite or to perform imaging (the latter during, e.g., alignment orregistration, or wafer inspection). The beam motion across the wafer 200can be, for example, vector scanning to a target feature or “care-area”containing a target feature, and raster scanning across the targetfeature while writing or inspecting. Preferably, each column 206 has itsown detector and control computer. Vector-raster scanning, care-areas,and use of multiple control computers local to respective columns aredisclosed in U.S. Pat. No. 9,466,463, which is incorporated herein byreference.

As mentioned above, after e-beams 204 write features to a resist-coatedsubstrate, the substrate is typically treated with resist developmentfollowed by etch steps in order to complete the writing process.(Herein, the immediate results of e-beam writing are called “features”,and continue to be called “features” throughout the patterning process,including after non-radiative steps, e.g., develop and/or etch.)

Herein, in some instances, develop and/or etch and/or other steps arenot explicitly described with respect to lithography and inspection. Itwill be understood by those skilled in the art that these steps (e.g.,develop and etch) are performed when appropriate, and can be omittedfrom discussion for clarity of explanation. Inspection (also referred toherein as “imaging”) of features on the substrate occurs after writing.

Generally, in resist development, the resist coated substrate isimmersed in or otherwise in contact with liquid chemical (resistdeveloper solution), followed by rinsing. Certain properties of theresist are changed by e-beam exposure such that the e-beam-exposed areaeither becomes soluble in resist developer solution (“positive” resist,which is insoluble until exposed to e-beams) or becomes insoluble inresist developer solution (“negative” resist, which is soluble untilexposed to e-beams). When a positive resist is exposed to e-beams, theunexposed portions remain insoluble, and will be left intact after thesubstrate is washed with resist developer solution. When a negativeresist is exposed to e-beams, the unexposed portions remain soluble, andwill be washed away by resist developer solution, leaving thee-beam-exposed portions intact.

As a result of resist development, a pattern will emerge on thesubstrate comprising many features written by the e-beam lithographytool. E-beams can then be used to inspect these features for defects.Inspection after development is also known as after-develop inspection(ADI).

Etch follows resist development. In etching, material exposed to theetch environment is removed, while material protected by developedresist is not etched. Inspection after etch is also known as after-etchinspection (AEI).

Both lithography (optical, e-beam and otherwise) and etch can introduceprocess-dependent defects to the patterned substrate. Generally,process-induced defects are defects introduced during wafer handling,resist spin and heating, lithography, resist development, etch,deposition, inspection, implantation, thermal processing, andchemical-mechanical polishing.

FIG. 2B shows an example of a wafer 200. The wafer 200 (or othersubstrate) is written or image data is gathered (beams are emitted)using columns 206 (columns 206 are shown via their center positions,represented here as plusses). Example die 208 size and column 206center-to-center spacing 210 (column separation) are shown. A regulargrid of columns 206 can use different spacing 210 in different(orthogonal) directions. Die 208 size and column separation 210 are notrequired to (and generally, will not) correspond. Column separation 210generally corresponds to the substrate area 202 targetable by beams 204emitted from respective columns 206.

Wafer 200 patterning and inspection using electron beams 202 can be madehighly parallelized by using multiple electron beams 202. Electron beams202 emitted by columns 206 in a multiple column 206 array can beindependently and simultaneously scanned across the wafer 200 usingelectrostatic deflectors, preferably using distributed column controlsystems (e.g., local column control computers, as described hereinabovewith respect to FIG. 2A).

The multiple column 206 array comprises electron beam columns 206arranged in a regular grid. For example, column 206 arrays withcenter-to-center column spacing 210 of 30 mm×30 mm have beenimplemented, though other column spacings 210 (e.g., 24 mm×33 mm) canalso be used.

A column 206 can be configured to scan a die 208 (IC), part of a die208, or multiple dies 208 during inspection. Each die 208 can be scannedby one or more columns 206, depending on the column 206 writing area202. The “writing area” is the area to which the column 206 can deflectits beam to obtain images or write pattern (depending on thecapabilities of the column 206), taking into account wafer stagemovement.

FIG. 2C schematically shows an example of a miniature e-beam column 220comprising an electron gun 222, including an electron source andelectron gun lens; deflection assembly 224; and main lens 226. Aminiature e-beam column 220 can also include, for example, deflectors,apertures, blankers, other electron-optical components, column controlelectronics, electron detectors or other sensors, and/or other elementsfor column 220 operation, maintenance, and testing.

FIG. 2D shows an example of an e-beam substrate patterning and/orinspection system 230. This e-beam system comprises an array 232 ofminiature e-beam columns 220, as well as a wafer loading/unloadingmechanism 234 and a wafer stage 236. Other sub-systems that are used forsubstrate patterning and/or inspection include control electronics,vacuum systems, alignment systems, vibration isolation and magneticshielding.

FIG. 2E shows an example of a uni-directional (1-D) layout process usingboth optical and electron beam lithography. “1-D” refers to 1-D griddeddesign rule.

Apparent resolution limits of optical systems have resulted in a processof simplification of integrated circuit layouts in order to ensureprintability as design rules shrink. At one time, pattern design commonwisdom allowed lines to run in virtually any direction. Later, patterndesign was largely restricted to perpendicular lines, often referred toas Manhattan geometries. As feature sizes shrink further, opticalpattern design can advantageously be restricted to lines running in asingle direction, with features perpendicular to the 1-D optical designformed in a complementary lithography step known as “cutting”. Thecomplementary step can be performed using a charged particle beamlithography tool comprising an array of columns—for example,electrostatically controlled miniature electron beam columns.

It is common to pattern the layout of 1-D designs by separating the 1-Ddesign layout database into lines and cuts. A 1-D layout 242 isseparated in the design layout database into a “line pattern” 244 and a“cut pattern” 246. The design layout database contains the informationneeded by lithography tools to pattern one or more layers on asubstrate. A line pattern 244 generally comprises an array ofunidirectional lines 248. Cut patterns 246 generally comprise line-cutsand holes 250.

Line patterns 244 are typically written by an optical lithographysystem, which can be followed by other process steps to increase thedensity of lines on the substrate 252. Cut patterns can be written bye-beam lithography 254 (e.g., miniature e-beam column lithography). Suchuse of e-beam lithography (which can also write via holes and contactholes) is also called complementary e-beam lithography, or CEBL. Thecombination of the line-forming process followed by line-cuts writtenwith CEBL to pattern a substrate layer is called complementarylithography. Optical masks for use in complementary lithography can bemade without any information about the cuts. CEBL generally uses onlythe cut database.

The optically-printed 252 line pattern 248 and the e-beam-written 254cut pattern 250 combine to form a 1-D layer 256 on the substrate thatcorresponds to the 1-D pattern 242 specified by the design layoutdatabase. Separating the pattern 242 this way uses the respective uniquecapabilities of optical lithography and e-beam lithography. Opticallithography can efficiently print uniform parallel lines over a largearea of a substrate. E-beam lithography inherently can write smallerfeatures more effectively than an optical lithography tool.

FIG. 2F schematically shows an example of a 1-D layout pattern 260.Here, line patterns 244 (printed by an optical lithography system) areshown as horizontal lines 262, while cut patterns 246 (written by, forexample, a CEBL system) are shown as (generally, much shorter) verticallines 264. Example spacing and line/cut widths are shown; other spacingand widths can be used (e.g., in more advanced processes).

FIG. 2G shows an example of a complementary lithography process 270. Oneor more multiple, miniature-column, e-beam lithography systems 230 areused in combination with an optical lithography system 272 and otherwafer processing tools (e.g. resist development and etch tools) topattern a wafer layer. Here, optical lithography tools 272 expose 2741-D lines 248. (Several other processing steps not shown in this figuretypically follow, e.g., involving resist and hard masks. Every othermention of “mask” herein refers specifically to optical masks, i.e.,masks used by an optical lithography system to expose a pattern.) E-beamlithography systems are then used to write 254 patterns 250 such as linecuts and holes. An etch tool 276 is used to etch 278 the resist,exposing the features written 254 by the e-beam tool 230.

Generally, e-beam lithography systems can write with higher resolutionthan optical lithography systems. However, in e-beam lithography,features are generally written serially (by individual beams), one at atime, as opposed to lithographic printing of a much larger area withoptical tools using masks.

FIGS. 2H and 2J show examples of prior art registration marks. Thesemarks can also be used as alignment marks.

FIG. 2I shows an example of prior art alignment mark placement. Chipmarks 280 are located within dies, while global marks 282 are located onthe stage. Note that beam x-axis 284 and beam y-axis 286 are notnecessarily parallel to (respectively) stage x-axis 288 and stage y-axis290.

Wafer or substrate “alignment” is defined herein as the action ofpositioning a wafer or other substrate with respect to the coordinatesystem of a lithography, inspection, or other process tool. Marks on thewafer or substrate that facilitate this process are called “alignmentmarks” or “alignment targets”.

“Pattern registration” (or “registration”) is defined herein aspositioning a subsequent pattern on the wafer or substrate with respectto a previous pattern on the wafer or substrate. Marks on the wafer orsubstrate that facilitate this process are called “registration marks”or “registration targets”. “Pattern overlay” is the measured errorresulting from inaccuracy of the registration process.

Generally, registration errors increase as distance from alignment andregistration targets increases, over time, and as beam deflections areperformed. Improving locality (in space and time) of registration toactive material processing and imaging locations tends to reduceaccumulated registration drift, reduce pattern overlay errors andimprove process and imaging fidelity, thereby improving yield.

Cross-like or other fiducial marks have historically been used toregister and/or align a single column. FIG. 2H is an example of apreviously used wafer alignment mark. FIG. 2I is an example of apreviously used reticle alignment mark.

SUMMARY

The present application discloses new approaches to systems, devices andmethods for writing and inspecting a substrate, using Hadamard targetsto align the substrate with a coordinate system of the correspondingtool, and/or to register patterns to be written or inspected withpreviously written pattern layers.

In particular, the inventors have discovered that, in a charged particlebeam column array context, beam alignment and registration performedusing multiple Hadamard targets distributed across the surface of asubstrate allows charged particle beam lithography and inspection toolsto achieve superior resolution and accuracy in practice, improving yieldrate.

The inventors have also discovered that Hadamard targets written smallenough, and with a high enough order that at least some blocks can beeffectively imaged at a default beam resolution while at least one blockcontains one or more features at or smaller than a threshold resolution(e.g., a resolution using default parameters, or a theoretical beamresolution limit for imaging), can be used to generate a variety ofcharged particle beam and beam column performance metrics usable for,e.g., extremely rapid calibration, column-to-column matching, and columnlife cycle management.

The inventors have also discovered that, by writing numerous (preferablyHadamard) targets to an edge-proximal portion of a substrate from whichresist is typically removed prior to lithography, superior position andorientation information regarding pattern layers previously written tothe substrate can be preserved, improving alignment and registrationaccuracy, as well as yield rate.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosed inventions will be described with reference to theaccompanying drawings, which show important sample embodiments and whichare incorporated in the specification hereof by reference, wherein:

FIG. 1 shows an example process for wafer alignment.

FIG. 2A shows an example of a wafer being scanned by multiple electronbeams emitted by respective beam columns.

FIG. 2B shows an example of a wafer.

FIG. 2C schematically shows an example of a miniature e-beam column.

FIG. 2D schematically shows an example of an e-beam substrate patterningand/or inspection system.

FIG. 2E shows an example of a 1-D layout process.

FIG. 2F schematically shows an example of a 1-D layout pattern.

FIG. 2G shows an example of a complementary lithography process.

FIG. 2H shows an example of a prior art registration mark.

FIG. 2I shows an example of prior art alignment mark placement.

FIG. 2J shows an example of a prior art registration mark.

FIG. 3 schematically shows an example of a Hadamard pattern generatedusing the Hadamard transform.

FIG. 4 schematically shows an example of a wafer with Hadamard targetsdistributed across its surface.

FIG. 5 schematically shows an example of Hadamard targets distributedacross a writing area comprising multiple stripes.

FIG. 6A schematically shows an example of Hadamard targets distributedacross a stripe.

FIG. 6B schematically shows an example of Hadamard targets distributedacross a frame comprising multiple scan fields.

FIG. 7A schematically shows an example of Hadamard targets distributedacross an e-beam scan field.

FIG. 7B schematically shows an example of Hadamard targets distributedacross an e-beam scan field.

FIG. 8A shows an example process for aligning multiple e-beam columnsfor substrate lithography.

FIG. 8B shows an example process for aligning multiple e-beam columnsfor substrate inspection.

FIG. 9 shows an example process for substrate alignment.

FIG. 10A shows an example process for improving pattern recognitioncorrelation of Hadamard targets.

FIG. 10B shows an example process for improving signal-to-noise ratio ofHadamard targets.

FIG. 11 shows an example process for correcting distortions.

FIG. 12 shows an example process for pattern registration.

FIG. 13 shows an example process for patterning high-order Hadamardtargets.

FIG. 14 shows an example process for inspection tool parameteroptimization using high-order Hadamard targets.

FIG. 15 shows an example process for wafer inspection.

FIG. 16 shows an example process for improving critical dimension (CD)and overlay metrology.

FIG. 17A schematically shows an example of nested Hadamard targets.

FIG. 17B schematically shows an example of nested Hadamard targets.

FIGS. 18A, 18B and 18C schematically show examples of conventionaloverlay marks nested in symmetric Hadamard target blocks.

FIG. 19 shows an example process flow for e-beam lithography andinspection.

FIG. 20A schematically shows an example of Hadamard target blockswritten locally to features comprising or used to write electronicallyfunctional portions of a substrate-borne device.

FIG. 20B schematically shows an example of Hadamard target blockswritten locally to features comprising or used to pattern electronicallyfunctional portions of a substrate-borne device.

FIG. 20C schematically shows an example of Hadamard target blockswritten such that one or more sub-blocks of said blocks will comprise orbe used to pattern electronically functional portions of asubstrate-borne device.

FIG. 20D schematically shows an example of a designated portion ofpattern comprising or used to write electronically functional features,wherein that portion is designated for use as a Hadamard target block.

FIG. 21A shows an example process for writing and/or imaging asubstrate.

FIG. 21B shows an example process for writing and/or imaging asubstrate.

DETAILED DESCRIPTION OF SAMPLE EMBODIMENTS

The numerous innovative teachings of the present application will bedescribed with particular reference to presently preferred embodiments(by way of example, and not of limitation). The present applicationdescribes several inventions, and none of the statements below should betaken as limiting the claims generally.

The present application discloses new approaches to systems, devices andmethods for writing and inspecting a substrate, using Hadamard targetsto align the substrate with a coordinate system of the correspondingtool, and/or to register patterns to be written or inspected withpreviously written pattern layers.

In particular, the inventors have discovered that, in a charged particlebeam column array context, beam alignment and registration performedusing multiple Hadamard targets distributed across the surface of asubstrate allows charged particle beam lithography and inspection toolsto achieve superior resolution and accuracy in practice, improving yieldrate.

The inventors have also discovered that Hadamard targets written smallenough, and with a high enough order that at least some blocks can beeffectively imaged at a default beam resolution while at least one blockcontains one or more features at or smaller than a threshold resolution(e.g., a resolution using default parameters, or a theoretical beamresolution limit for imaging), can be used to generate a variety ofcharged particle beam and beam column performance metrics usable for,e.g., extremely rapid calibration, column-to-column matching, and columnlife cycle management.

The inventors have also discovered that, by writing numerous (preferablyHadamard) targets to an edge-proximal portion of a substrate from whichresist is typically removed prior to lithography, superior position andorientation information regarding pattern layers previously written tothe substrate can be preserved, improving alignment and registrationaccuracy, as well as yield rate.

The disclosed innovations, in various embodiments, provide one or moreof at least the following advantages. However, not all of theseadvantages result from every one of the innovations disclosed, and thislist of advantages does not limit the various claimed inventions.

-   -   improved yield rate;    -   improved beam resolution and accuracy;    -   improved alignment and registration accuracy;    -   improved layer-to-layer metrology;    -   reduced pattern overlay error;    -   Hadamard targets provide improved beam drift mitigation and        compensation;    -   Hadamard targets are easily configured for miniature electron        beam column deflection field calibration (intra-column), and        offset calibration and correction (inter-column);    -   per-column alignment and registration can be performed from        imaging and identification of a single Hadamard target block;    -   Hadamard targets are selectable for high signal-to-noise ratio        in a compact footprint;    -   Hadamard targets provide arbitrary target size and complexity        scalability;    -   Hadamard targets provide arbitrarily complex security code        options;    -   Hadamard targets provide superior target pattern fidelity;    -   Hadamard targets provide improved resilience of targets to        optical-proximity and edge loading effects;    -   high-order Hadamard targets can be used to perform extremely        rapid design of experiments (DOE) on beam parameters, and for        various beam performance metrics.

Some exemplary parameters will be given to illustrate the relationsbetween these and other parameters. However it will be understood by aperson of ordinary skill in the art that these values are merelyillustrative, and will be modified by scaling of further devicegenerations, and will be further modified to adapt to differentmaterials or architectures if used.

Multiple-column charged particle beam lithography and inspection offersincreased throughput and circumvention of local charged particle doselimitations on semiconductor patterns, micro-electro-mechanical systems(MEMS), and other substrate-related device structures. Multiple-columntechnology requires substrate alignment and registration to properlyplace and orient new pattern layers with respect to underlying patternswhile operating in a massively parallel, independent mode. Further, inhigh-throughput multiple-electron-beam systems, beam positioning driftproblems can arise due to factors such as thermal distortion andfabrication errors of electron optics. Periodic recalibration usingalignment and/or registration marks on the wafer can be used to achieveconsistent beam placement accuracy and improve yield rate.

Embodiments disclosed herein enable superior alignment and registrationusing uniquely identifiable Hadamard patterns as registration andalignment targets. These targets can be scaled spatially and accessedtemporally as required to meet demanding specifications for futuregenerations of lithography and inspection. Disclosed embodiments alsoenable additional applications in the areas of lithography, inspection,and design optimization and in the areas of process control and yieldimprovement.

High-order Hadamard patterns can also be utilized to quickly obtain avariety of persistent and/or immediately actionable beam columnperformance metrics.

Generally, Hadamard target 402 patterns can be selected so that some orall blocks 302 comprising a Hadamard target 402 pattern comprise uniquepatterns with respect to each other (i.e., some or all of the individualblocks 302 in a Hadamard target 402 are different from each other block302 in that Hadamard target).

Registration marks and alignment marks are collectively referred toherein as “targets” (where “target” is used as a noun). Those ofordinary skill in the art of charged particle beam lithography willunderstand from context where “target” is used as a verb, in which caseit refers to direction (using, e.g., electrostatic deflection) ofcharged particle beams to particular locations on a substrate surface.

Embodiments disclosed herein use one or more charged particle beamcolumns to pattern and/or inspect a substrate. Preferred embodiments usearrays of electrostatically controlled e-beam mini-columns. In someembodiments, these columns can be configured to write with chargedparticle beams on substrates and/or (either or both) image features onsubstrates.

“Substrate” is defined herein as a workpiece having a composition andshape amenable to patterning and deposition of one or more layers ofmaterial thereupon using techniques applicable to semiconductor devicefabrication, such that functional devices can be produced therefrom. Awafer 200 is a type of substrate.

The “design layout database” is the database specifying physical layoutto be patterned on the substrate (e.g., for electronic semiconductordevices, a database of electrical designs that have been rendered intophysical layouts).

Fully automated beam 204 targeting based directly on a design layoutdatabase is preferred. Beam 204 targeting “based directly on (or indirect dependence on) a design layout database” is defined to mean thatduring patterning, local column controllers automatically accessportions of the design layout database relevant to corresponding writingareas 202 and interpret the design layout database directly into beamcolumn 206 control instructions for immediate use specifying beamdeflection, beam dwell timing, beam blanking timing, beam shape and/orbeam landing energy.

Direct deposition of material by a charged particle beam tool isdisclosed by, for example, U.S. Pat. No. 9,453,281, which isincorporated herein by reference. Direct removal of material by acharged particle beam tool (e.g., direct etch) is disclosed by, forexample, U.S. Pat. No. 9,466,464, which is incorporated herein byreference. Direct modification of material by a charged particle beamtool is disclosed by, for example, U.S. patent application Ser. No.14/980,884, which is incorporated herein by reference. Systems, methodsand tools for etching cut features and depositing pattern material intosaid cut features within a single pass is disclosed by, for example,U.S. patent application Ser. No. 15/171,922, which is incorporatedherein by reference. Direct deposition, subtraction and modification arealso collectively called “direct writing”, which generally refers topattern writing using one or more charged particle beams, wherein thebeams cause prompt effect (deposition, subtraction or modification) onsubstrate or substrate surface material as a direct result of affect (onsubstrate or substrate surface material, or on material adsorbed by thesubstrate surface) by the charged particle beams.

As used herein, “writing” (or “patterning”) a substrate refers to anyprocess which expresses specified pattern in or on the substrate(including material deposited on the substrate surface), expressedthrough any physical or chemical property of said substrate or depositedmaterial. With respect to charged particle beams 204 targeted in directdependence on a design layout database, “writing” includes, for example,direct writing, CEBL, and other techniques that do or do not use resistand resist-related processes.

Image capture (imaging) can be performed in various ways, e.g., in themanner of a scanning electron microscope (SEM), or using a combinationof vector and raster scanning Captured images of registration marks canbe used for, for example, alignment of columns, registration with otherpatterns on the substrate, overlay with previously formed patterns,measurement of critical dimensions, and characterization of defects.This technology also applies to multi-column arrays for the purposes ofmitigating beam drift, improving beam placement accuracy, enhancingoverlay accuracy, and increasing overall patterning and process yield.

Hadamard and Walsh transforms are examples of a class of generalizedFourier transforms. They return values of −1 and +1, interpretable asbinary 0's and 1's (write a pixel and do-not-write a pixel) for purposesof the inventions herein.

A “Hadamard matrix”, as used herein, is the matrix of outputs of thefunctions or algorithms used to generate a Hadamard target 402; see,e.g., FIG. 3. The “transform output vectors”, as used herein, are eitherthe individual rows or the individual columns of entries in a Hadamardmatrix, but not both with respect to permutations performed to generatea single Hadamard target pattern. “Block” 302 and “sub-block” 308 aredefined below. The “binary correlation” between a pair of blocks 302 ina Hadamard target 402 is defined as the sum of the products of the ±1values in sub-blocks 308 (cells) in the same (row, column) location(having the same x 310 and y 312 indices) in pairs of different blocks302 in a Hadamard target 402. “X and y edge information” refers hereinto edge information corresponding to edges running in x and ydirections, i.e., generally orthogonal directions on the surface of asubstrate.

A “Hadamard target” 402 is defined herein as a pattern generated usingfunctions or algorithms used to calculate the Hadamard and/or Walshtransform(s) (e.g., as shown in Equation 1 below); wherein transformoutput vector reordering (per-vector reordering, not within vectors) ispermitted; wherein the N rows and columns that would have the fewestsign changes (write/do-not-write transitions) after sequency reorderingof the Hadamard matrix can be removed; wherein additional permutationsare then permitted if they preserve edges (write/do-not-writetransitions) corresponding to adjacent sub-blocks within a block; andwherein transposition of entire blocks is then permitted, as discussedbelow with respect to FIG. 3. (Sequency ordering arranges the transformoutput vectors in order of the number of sign changes per vector.)Unmodified Hadamard transform outputs have a large amount of x and yedge information and block-to-block pattern uniqueness. Those ofordinary skill in the art of substrate patterning and inspection usingcharged particle beams will understand that such reordering andpermutation should be chosen to retain sufficient x and y edgeinformation and block-to-block pattern uniqueness to enhancesignal-to-noise ratio and enable rapid determination of which block 302is being imaged during inspection. Preferably, the binary correlationbetween pairs of blocks 302 in a Hadamard target 402 should be 0 toenhance block-to-block pattern uniqueness.

For example, the Hadamard pattern 300 shown in FIG. 3 corresponds to asequency-ordered Hadamard matrix of size 16×16. A Hadamard target 402can advantageously be selected as the pattern shown in FIG. 3 other thanthe portions indexed by u=0 or v=0 (i.e., 3×3 Hadamard array 314).

A mathematical description of Hadamard targets 402 is given below inEquations 1 and 2 for the case of N=4, wherein blocks 302 have indices uand v with values from 0 to N−1, and sub-blocks 308 have indices x and ywith values from 0 to N−1, as shown in FIG. 3. This is a special case; Ncan be (generally) any positive integer, though preferably N≥4. As usedherein (for u 304, v 306, x 310 and y 312 as described below withrespect to FIG. 3), a “block” 302 is the portion of a Hadamard target402 indexed by a single (u,v) pair; and a “sub-block” 308 is a singlecell, corresponding to a single row and a single column in the Hadamardtarget 402 (indexed by the quadruplet (u,v,x,y) in FIG. 3). (The indicesu, v, x, and y correspond to the indices u 304, v 306, x 310 and y 312with respect to an unpermuted Hadamard matrix generated using Equations1 and 2.)

$\begin{matrix}{{H\left( {u,v} \right)} = {\frac{1}{4}{\sum\limits_{x = 0}^{3}{\sum\limits_{y = 0}^{3}{{f\left( {x,y} \right)}\left( {- 1} \right)^{\sum\limits_{i = 0}^{1}{\lbrack{{{b_{i}{(x)}}{p_{i}{(u)}}} + {{b_{i}{(y)}}{p_{i}{(v)}}}}\rbrack}}}}}}} & \left( {{Equation}\mspace{14mu} 1} \right) \\{{f\left( {x,y} \right)} = {\frac{1}{4}{\sum\limits_{u = 0}^{3}{\sum\limits_{v = 0}^{3}{{H\left( {u,v} \right)}\left( {- 1} \right)^{\sum\limits_{i = 0}^{1}{\lbrack{{{b_{i}{(x)}}{p_{i}{(u)}}} + {{b_{i}{(y)}}{p_{i}{(v)}}}}\rbrack}}}}}}} & \left( {{Equation}\mspace{14mu} 2} \right)\end{matrix}$

The variables and constants in Equations 1 and 2 above are defined asfollows:

-   -   Indices u, v, x, and y run from 0 to 3 (0 to N−1)    -   p0(u)=b1(u)    -   p1(u)=b1(u)+b0(u)    -   p0(v)=b1(v)    -   p1(v)=b1(v)+b0(v)    -   b0(x) is the 0^(th) bit in the binary representation of x    -   b1(x) is the 1^(st) bit in the binary representation of x

Generalized equations for the Walsh-Hadamard transform are set forth in,for example, the Gonzalez and Woods “Digital Image Processing”reference, fully cited below and incorporated herein by reference.

Hadamard and/or Walsh transform(s) are used as generating functions tocreate Hadamard target patterns and reference patterns for Hadamardtargets 402 already written to a substrate.

Hadamard (and/or Walsh) matrices used to create Hadamard targets 402 arecomputable using the generating functions (e.g., Equations 1 and 2) andare, therefore, easily integrated with a “cutting” database supplied tothe substrate patterning or inspection tool. Noisy reference images areunnecessary.

Preferred embodiments use a plurality of Hadamard targets 402 to meetanticipated next-generation alignment and pattern registrationrequirements for both inspection and patterning. In semiconductor waferinspection, precise location of defect position is critical forroot-cause analysis and yield estimation. In semiconductor patterning,precise location of successive patterns is critical to the formation offunctional circuits.

Other registration marks, such as checkerboard patterns, gratingpatterns, box-in-box patterns, bar-in-bar patterns, and otherregistration (and alignment) marks can also be used in addition toHadamard targets 402 and/or as edge-proximal targets.

Once targets are imaged, a pattern recognition algorithm measuring,e.g., the amount of correlation between (1) the captured image and (2) atemplate comprising a computer-generated template (used in preferredembodiments; this can be pre-computed) or a stored image, is used torecognize imaged target pattern(s). Pattern recognition algorithmstypically generate a mathematical “correlation score” to quantify thegoodness of the match between the captured image and the template. Whenimaging Hadamard targets 402, beam columns 206 preferably image at leastsufficient x and y edge information to distinguish the resulting signalfrom random noise in the captured image.

Imaging and analysis for pattern recognition of Hadamard target 402features by multi-column e-beam tools can be made automatic using, forexample, substantially the same beam columns and stages, and the samedesign layout database, for writing and imaging said Hadamard targets402, as disclosed in U.S. Pat. No. 8,999,627 (definitions of“substantially the same” beam columns and “substantially the same”stages as provided therein are adopted herein), which is incorporatedherein by reference.

“Offsets” are defined herein as adjustments made to parameters used totarget e-beam columns 206 to locations specified by the design layoutdatabase so that actual locations where the beam intersects thesubstrate match (preferably, as closely as possible) actual locationswhere pattern should be written (for substrate patterning, e.g., toproperly correspond to pattern locations in previously-written layers)or has been written (for inspection). It will be apparent to one ofordinary skill in the arts of charged particle beam substrate patterningand inspection that statements and claim language herein referring tooffsets with respect to beams rather than columns are shorthandreferences to offsets applied to parameters used to target correspondingcolumns projecting the beams being discussed or claimed.

FIG. 1 shows an example process for wafer alignment. In preferredembodiments, targets are prepared for use in wafer alignment (orregistration) 102 as follows. After a wafer 200 is loaded into the track104, resist is spun on. Edge-bead removal following resist spin-on isminimized 106 in order to leave sufficient resist in an edge-proximalportion of the wafer 200 to allow that edge-proximal portion to bewritten with pattern.

After the wafer 200 is prepared with resist, an e-beam array patternsthe wafer 200 with edge Hadamard targets 406 and inner Hadamard targets404 in step 108. “Edge targets” are defined herein as alignment and/orregistration marks (Hadamard targets 402 and/or other patterns)patterned on edge-proximal portions of the wafer 200 from which most orall resist will be removed following resist spin-on when preparing towrite later pattern layers. “Inner targets” are defined herein astargets (Hadamard targets 402 and/or other patterns) patterned onnon-edge-proximal portions of the wafer 200 (e.g., portions of the wafer200 that will comprise dies 208 or that will be between die regions whenthe wafer 200 is cut) that will remain covered by sufficient resist forpattern writing (generally, will be buried under resist) followingedge-bead removal after resist spin-on when preparing to write laterpattern layers (e.g., following step 116). Edge targets are alignmentand/or registration marks that are exposed and available for imaging foralignment and/or registration during later EBL (e-beam lithography)pattern layer write iterations. After edge and inner Hadamard targets404, 406 are written 108, the resist is developed, the substrate isetched, and the resist is stripped 110, leaving behind the writtenpattern (including the written edge and inner Hadamard targets 404,406).

Once the targets are prepared 102, they can be used for wafer alignmentand/or pattern registration.

In preferred embodiments, wafer alignment 112 for substrate patterningand/or inspection is performed as follows. A wafer 200 with multipleHadamard targets 402 previously prepared 102 is loaded into an e-beamtool. (Herein, a wafer 200 with multiple Hadamard targets 402 previouslyprepared 102 refers to a wafer 200 with Hadamard targets 402 located inmultiple different writing areas, i.e., of multiple different columns206 in an array of columns 206.) The e-beam tool then images the wafer200 (e.g., at and/or near expected Hadamard target locations based onthe design layout database) and locates edge and inner Hadamard targets404, 406 using design layout database correlation 114 (using patternrecognition, such as the “correlation score” described above).

The locations of the Hadamard targets 402 detected in step 114(corresponding to deflections of the e-beams by the respective emittingcolumns when imaging the Hadamard targets 402, and contemporaneous stagepositions) are stored for use in later steps. The wafer 200 is thenmoved to the track, resist is spun-on, and edge-bead removal isperformed to leave the edge-proximal portion of the wafer 200 on whichthe edge Hadamard targets 406 were written bare of resist 116 (e.g.,using standard edge-bead removal techniques). The wafer 200 is thenloaded into an e-beam tool (a combined EBL/EBI tool or an EBI tool—EBIstands for e-beam inspection). The EBI (imaging) functions of the e-beamtool are used to locate the edge Hadamard targets 406, and the resultingedge Hadamard target locations are mapped to the previously-writteninner Hadamard target locations 118 using the locations determined bythe imaging of step 114 (which indicate the relative spatial positionsof edge and inner Hadamard targets 404, 406). Target locationinformation and stage position information, from steps 114 and 118, arecombined to calculate offsets for the columns 206 in step 120 (e.g., bycomparing target locations as-written to target locations specified inthe design layout database; stage-related distortions are addressed withrespect to, e.g., FIG. 11). Edge Hadamard targets 406, carrying overbetween (resist spin-on and) writing iterations corresponding tosuccessive pattern layers, thus allow highly accurate e-beam columnalignment and registration, enabling reduced pattern overlay error andincreased yield rate.

Steps 118 and 120 can be repeated to perform alignment for latersubstrate patterning and inspection iterations.

Hadamard targets 402 can also be written by one or more charged particlebeams without using a resist layer; for example, using direct additionor direct subtraction. One of ordinary skill in the art of chargedparticle beam substrate patterning and inspection will understand thatimaging and alignment and/or registration can then proceed similarly asin resist layer-using processes. (This is generally true for embodimentsdisclosed herein with respect to writing and imaging of, andcalculations based on, Hadamard targets 402.) However, for processlayers where previously written Hadamard targets 402 remain imageable bybeams 204 (e.g., process layers not using a resist layer and in whichHadamard targets 204 remain exposed on the substrate surface), Hadamardtargets 402 can generally be imaged and used for registration (oralignment or other purposes) without mapping of edge target locations toinner target locations as discussed with respect to FIG. 1.

FIG. 3 schematically shows an example of a Hadamard pattern 300generated using the Hadamard transform. This Hadamard pattern 300corresponds to a sequency-ordered Hadamard matrix generated using theHadamard transform pair provided above as Equations 1 and 2 (N=4). Therearranged 4×4 array 300 of blocks 302 has indices u 304 and v 306, andembedded sub-blocks 308 with indices x 310 and y 312.

Generally, the most useful patterns for alignment and/or registrationare those that provide two-dimensional edge information (both x AND ydirections). Hadamard patterns are easily selectable for maximum x and yedge information (corresponding to edges running in x and y directions)to increase the signal-to-noise ratio of position estimates. TheHadamard pattern 300 shown in FIG. 3 includes a 3×3 Hadamard array 314(a 3×3 array of blocks 302 generated using the Hadamard transform) thatprovides a large amount of edge information in both x and y directions,and is preferred for use as a Hadamard target 402 for wafer alignmentand/or pattern registration.

Hadamard target patterns can be selected so that a single Hadamardtarget block 302 provides sufficient x and y edge information, when thatblock 302 is imaged, to locate the Hadamard target's 402 center block316 (and/or other blocks 302, for further imaging); and/or to performeffective registration and/or alignment; and/or to locate the Hadamardtarget 402 with respect to other Hadamard targets 402 on the wafer 200.Imaging additional Hadamard target blocks 302, and particularly asymmetric Hadamard target block 302 at or near the center of a Hadamardtarget 402 such as a center block 316, can further improve thesignal-to-noise ratio of position estimates.

Hadamard targets 402 are easily configured as rearrangements(transpositions) of their component blocks 302, generally withoutcompromising their utility as alignment and/or registration targets. Forexample, a Hadamard target 402 comprising a 3×3 Hadamard array 314, withnine (9) blocks 302, can have those blocks 302 rearranged in up to ninefactorial (9!), or 362,880, different ways. (Hadamard targets 402 withlarger numbers of blocks 302 can potentially have those blocks 302rearranged in even more ways.) This provides a large number of uniqueblock combinations to be used as, for example, identification orsecurity codes, indexable by, for example, a look-up table. These codescan be used, for example, to mark a product line, an individual wafer, awafer location, or an individual die, or to encode data (individually oras a group of coded targets).

The Hadamard pattern 300 shown in FIG. 3 is produced using N=4, but awide range of values of N are potentially useful. For example, higher Ncan be used to produce Hadamard targets 402 with increased and/or moredensely compressed x and y edge information.

FIG. 4 schematically shows an example of a wafer 200 with Hadamardtargets 402 distributed across its surface. FIG. 4 shows exampleplacement of both edge and inner Hadamard targets 404, 406. Hadamardtargets 402 can be written on the substrate at spacing corresponding tothe column separation 210, or with other regular or irregular spacing,and/or more densely, as shown below in FIGS. 5, 6A, 6B, 7A and 7B.

In preferred embodiments, Hadamard targets 402 are constructed such thateach block 302 has a known spatial vector separating it from the centralblock 316. Generally, imaging and locating one block 302 in a 3×3 blockarray 314 Hadamard target 402 is sufficient for accurately determiningthe location of the center (or central block 316) of the Hadamard target402. (Imaging and locating a block 302 can comprise imaging portions ofone or more blocks 302 until the boundaries of an individual block 302are determined.) Furthermore, each Hadamard target 402—including innerHadamard targets 404 and edge Hadamard targets 406—is separated by aknown (or calculable based on the design layout database) spatial vectorfrom the center of the other Hadamard targets 402 on a substrate, aswell as from the center of the substrate 408, and potentially from theedge of the substrate 410. These known vectors can be refined by imagingHadamard targets 402 to determine actual locations of the Hadamardtargets 402 as-written.

The outer edge of the resist layer 412 that remains after typicaledge-bead removal (leaving the edge-proximal region of the substratebearing edge targets 406 bare) can be considered a boundary betweeninner Hadamard targets 404 and edge Hadamard targets 406.

Hadamard targets 402 are easily configured for multi-column offsetcalibration and correction (inter-column): multiple columns 206 can beused to scan the same Hadamard target 402 for column-to-columnpositional correlation. This can be facilitated by placing one or moreHadamard targets 402 near junctions between column writing areas,enabling easy access and imaging by adjacent columns 206.

FIG. 5 schematically shows an example of Hadamard targets 402distributed across a writing area 202 comprising multiple stripes 502. Astripe 502 is the portion of the wafer 200 surface that an e-beam cantarget while the stage is moving predominantly in a single direction,i.e., before the stage moves laterally and switches predominantdirections to give the e-beam access to a different stripe 502. MultipleHadamard targets 402 can be located within a column's 206 writing area202 (across the scan field). Distribution of Hadamard targets 402 acrossthe column writing area 202 allows registration on the fly—that is,e-beams can visit nearby Hadamard targets 402 when convenient (e.g.,when a Hadamard target 402 is within the current scan field 604) duringa writing and/or imaging iteration in order to refine, repair or confirmaccurate pattern registration. Generally, the more Hadamard targets 402are distributed through a writing area 202, the more readily and/orfrequently registration or re-registration (or other proceduresdisclosed herein with respect to Hadamard targets 402) can be performed.

FIG. 6A schematically shows an example of Hadamard targets 402distributed across a stripe 502. Columns 206 can write patterns and/orinspect regions within a writing area 202 comprising multiple stripes502; stripes comprise multiple frames 602. A frame 602 is the portion ofthe wafer surface that an e-beam can target at a given time.

FIG. 6B schematically shows an example of Hadamard targets 402distributed across a frame 602 comprising multiple scan fields 604. Ascan field 604 is a portion of a frame, used for addressing purposes.

FIGS. 7A and 7B schematically show examples of Hadamard targets 402distributed across an e-beam scan field 604. Hadamard targets 402 can beregularly spaced within a scan field 604 as shown in FIG. 7A, or can beirregularly scattered across a scan field 604 as shown in FIG. 7B (thelatter would more likely be typical in a production wafer).

Hadamard targets 402 are easily configured for mini-column deflectionfield calibration and correction (intra-column). Deflection fieldcalibration (imaging Hadamard targets and calculating offsets based oncomparison between imaged targets and the design layout database) canperformed using Hadamard targets 402 distributed across frames 602 andacross scan fields 604.

FIG. 8A shows an example process for aligning multiple e-beam columns206 for substrate patterning 800. A wafer 200 with Hadamard targets 402previously prepared 102 is loaded into an e-beam tool. The e-beam toolthen locates the edge and inner Hadamard targets 404, 406 using designlayout database correlation 802. The locations of the Hadamard targets402 detected in step 802 are stored for use in later steps. The wafer200 is then moved to the track, resist is spun-on, and edge-bead removalis performed to leave the edge-proximal portion of the wafer 200 onwhich the edge Hadamard targets 406 were written bare of resist 804. Thewafer 200 is then loaded into an e-beam tool (a combined EBL/EBI tool oran EBI tool). The EBI (imaging) functions of the e-beam tool are used tolocate the edge Hadamard targets 406, and the resulting edge Hadamardtarget locations are mapped to the previously-written inner Hadamardtarget locations 806 using the locations determined by the imaging ofstep 802 (which indicate the relative spatial positions of edge andinner Hadamard targets 404, 406). Target location information and stageposition information, from steps 802 and 806, are combined to calculateoffsets for the columns 206 in step 808.

FIG. 8B shows an example process for aligning multiple e-beam columns206 for substrate inspection 810. A wafer 200 with Hadamard targets 402previously prepared 102 is loaded into an e-beam tool. The e-beam toolthen locates the edge and inner Hadamard targets 404, 406 using designlayout database correlation 812. Target location information and stageposition information are combined to calculate offsets for the columns206 in step 814.

FIG. 9 shows an example process for substrate alignment 900. Alignmentand registration can be performed using multiple Hadamard blocks 302 inone or more Hadamard targets 402, the blocks 302 having known offsets torespective Hadamard target central (or most-symmetric) blocks 316, toincrease alignment robustness and to reduce alignment overhead. Forexample, if there is a “near-miss” when an e-beam beam is vectored to(or otherwise deflected to target) a specific block 302 in a Hadamardtarget 402 to image that block 302, then imaging can be directed tolocate a unique pattern in the Hadamard target 402. The actual locationof the unique pattern, as imaged, allows the discrepancy betweendeflection parameters used for targeting, and deflection parametersrequired to image the intended target, to be determined. Thecorresponding e-beam column can then be controlled to either correctposition immediately or re-center and re-align based on design layoutdatabase information (e.g., using some or all of the Hadamard targetportion actually imaged, and/or by completing imaging of the block 302actually vectored to and/or of the block 302 containing the locatedunique pattern).

In some embodiments, as shown in FIG. 9, a wafer 200 with Hadamardtargets 402 previously prepared 102 is loaded into an e-beam tool. Onesof the e-beam columns 206 in the e-beam tool then locate a Hadamardtarget block 302 within a Hadamard target 402 in step 902; for example,by targeting a central (or most-symmetric) block 316 of a Hadamardtarget 402. The offset from the imaged block 302 to the central block316 of that Hadamard target 402 is then calculated 904 using the knownspatial vector between the two blocks 302. Using the calculated offset,the beam emitted by the e-beam column 206 is re-centered to target thecentral block 316 of that Hadamard target 402. That central block 316 isthen imaged to determine its location 906. Locations of central blocks316 determined by respective e-beam columns 206 can then be combinedwith stage position information to calculate offsets 908 for use by thee-beam columns 206 when targeting the substrate.

FIGS. 10A and 10B show example processes for improving patternrecognition correlation and signal-to-noise ratio of Hadamard targets402. A wafer 200 with multiple Hadamard targets 402 previously prepared102 is loaded into an e-beam tool, and one or more e-beam columns 206image multiple Hadamard target blocks 302 within one or more Hadamardtargets 402 in step 1002. The resulting image(s) can be compared with(preferably) a computer-generated template (or a stored image) todetermine which block 302 provides the best pattern recognitioncorrelation 1004. The image(s) produced in step 1002 can also beevaluated to determine image quality to determine which block's 302images result in the best signal-to-noise ratio 1006.

Block 302 imaging priority can be based on, e.g., a combination of thepattern recognition correlation and signal-to-noise ratio qualities ofHadamard target blocks 302 analyzed as discussed with respect to FIGS.10A and 10B. Which of the blocks' 302 images results in superior patternrecognition correlation and/or signal-to-noise ratio can be related to,for example, which of the blocks' 302 patterns in a Hadamard target 402has higher uniqueness, better image contrast, or more x and y edgeinformation.

FIG. 11 shows an example process for correcting distortions 1100. Awafer 200 with multiple Hadamard targets 402 previously prepared 102 isloaded into an e-beam tool, and one or more e-beam columns 206 imagemultiple Hadamard target blocks 302 at step 1102 within one or moreHadamard targets 402. The presence of distortion-related errors due to,e.g., translation, rotation, skew, magnification, and higher-orderdistortions, can be determined by correlating Hadamard target imageinformation with the design layout database 1104.

FIG. 12 shows an example process for pattern registration(layer-to-layer overlay). Layer-to-layer overlay metrology can beimproved using Hadamard targets 402 with overlay marks embedded withinthem (e.g., within a symmetric block). Embedding an overlay mark in asymmetric Hadamard target block 302 can be used to improve overlay markcentering and lessen proximity effects, thereby reducing overlaytool-induced-shift (TIS) and process dependent wafer-induced-shift(WIS).

In some embodiments, as shown in FIG. 12, a wafer 200 with multiple edgeand inner Hadamard targets 404, 406 previously prepared 102 is loadedinto an e-beam tool. The wafer 200 is also prepared with non-Hadamardpattern overlay marks embedded within multiple ones of the edge and ofthe inner Hadamard targets 404, 406. One or more e-beam columns 206image said edge and inner Hadamard targets 404, 406 to locate them usingdesign layout database correlation 1202. The overlay marks embeddedwithin the Hadamard targets 402 are also imaged to reduce error indetermining target location 1204. The wafer 200 is then moved to thetrack, resist is spun-on, and edge-bead removal is performed to leavethe edge-proximal portion of the wafer 200 on which the edge Hadamardtargets 406 were written bare of resist 1206. The wafer 200 is loadedinto an e-beam tool, which is used to locate the edge Hadamard targets406 at step 1208 (using imaging and pattern recognition). The e-beamtool is also used to image the overlay marks embedded within edgeHadamard targets 406. The resulting edge Hadamard target 406 and overlaymark locations are mapped to the previously-written inner Hadamardtarget 404 and embedded overlay mark locations 1210 using the locationsdetermined by the imaging of steps 1202 and 1204. Target locationinformation and stage position information, from steps 1202, 1204, 1208and 1210 are combined to calculate offsets for the columns 1212.

FIG. 13 shows an example process for patterning high-order Hadamardtargets 402. “High-order Hadamard targets” 402 is defined herein asHadamard targets 402 generated using N≥5 (for Hadamard and/orcorresponding Walsh transform generating functions such as Equations 1and 2). Preferably, high-order Hadamard targets 402 have order N muchgreater than 4, such as N≥10, to make it easier to configure high-orderHadamard targets 402 so that (generally) with initial beam parametervalues and stable columns 206, at least one block 302 will be correctlyimaged and at least one block 302 will not be correctly imaged. Thisprovides, for example, both a baseline result for performancecomparison, and room for differentiation in measured performance.

High-order Hadamard targets 402 can be used to perform a variety offunctions, for example: stress testing design-for-manufacturability(DFM) and design-for-yield (DFY) strategies (for example, correlationscores with respect to templates could be fitted to a response surfaceallowing location of optimal parametric ranges); rapiddesign-of-experiments (DOE) optimization of e-beam parameters such asbeam energy (landing voltage), beam focus, exposure time, beam current,beam size, beam initial position, and beam scan rate (and other chargedparticle detection and deflection parameters); initial e-beamcalibration; immediate flagging of column 206 instability based on acolumn's 206 off-trend or sub-threshold performance results when imaging(or writing) a high-order Hadamard target 402; providing a performancemetric for column-to-column comparison; column 206 performance matching;providing a system-wide imaging quality metric; providing a persistentcolumn 206 performance metric allowing analysis of the evolution ofcolumn 206 characteristics over time, e.g., per-column 206 andper-column-array; and as a test pattern for automatic e-beam parameteroptimization for patterning (e.g., automatic e-beam parameteroptimization as disclosed in U.S. Pat. No. 8,999,627, incorporatedherein by reference). These applications can be performed using, forexample, size 20×20 block array Hadamard target(s) 402 (N=20) configuredto contain blocks 302 with features smaller than normal design rules;advantageously, features in the size range associated with “killerdefects” (defined as defects that result in loss of devicefunctionality).

Beam performance can be measured by, for example, resolution, contrast,signal-to-noise ratio, edge-sharpness, and deflection accuracy.

In some embodiments, as shown in FIG. 13, preparation of a wafer 200with high-order Hadamard targets 402 written thereon 1300 can beperformed as follows. A wafer 200 is loaded into a track 1302, resist isspun on, and edge-bead removal is minimized 1304. High-order Hadamardtargets 402 are written on the wafer 1306, comprising either or both ofedge high-order Hadamard targets 406 and inner high-order Hadamardtargets 404. After high-order Hadamard targets 402 are written 1306, theresist is developed, the substrate is etched, and the resist is stripped1308 to leave behind the written pattern.

FIG. 14 shows an example process for inspection tool parameteroptimization using high-order Hadamard targets 402. Correlation ofinspection tool images of high-order Hadamard targets 402 withpre-computed pattern templates or reference images can be used to selectoptimal inspection tool settings, and to test sensitivity and accuracy,using DOE methods.

In embodiments as shown in FIG. 24, a wafer is prepared with high-orderHadamard targets 402 written thereon 1300. To perform DOE inspectiontool parameter optimization, the wafer 200 is then loaded into aninspection tool, and the tool's e-beams are used to locate respectivehigh-order Hadamard targets 402 using design layout database correlation1402. The tool progressively images smaller and smaller features in thehigh-order Hadamard targets 402 at step 1404 (or blocks 302 that areotherwise progressively more difficult to correctly image, e.g., withdecreasing average or minimum feature sizes, and/or with increasingmaximum density of x and/or y edge information in all or portions of theblocks 302, and/or with an increasing number of write/do-not-writetransitions), correlating feature images with computer generatedtemplates or reference images and using correlation results to determinewhether the inspection tool correctly (e.g., accurately) images saidprogressively smaller features 1406. If the tool is able to correctlyimage the features, imaging continues to progress towards smallerfeatures; and if the tool is able to correctly image sufficiently smallfeatures (e.g., meeting a pre-set standard) 1408, then the inspectiontool can be deemed sufficiently sensitive and accurate for defectinspection with current parameters 1410. However, if the tool is notable to correctly image sufficiently small features, the tool'sparameter settings are adjusted to stochastically improve toolperformance 1410, and the process is repeated, preferably from step 1404on.

FIG. 15 shows an example process for wafer 200 inspection. A wafer 200written with pattern to be inspected and high-order Hadamard targets 402(preferably at least one high-order Hadamard target 402 per column 206to be used in inspecting for defects) is loaded into an inspection tool;and the wafer 200 is imaged to locate the high-order Hadamard targets200 using design layout database correlation 1502. The high-orderHadamard targets 402 are imaged, and corresponding offsets arecalculated, to improve alignment 1504. The wafer 200 is inspected fordefects, and defect location data is saved with respect to nearestregistration targets (preferably Hadamard targets 402) 1506. Theinspection data is analyzed to classify possible defects 1508, andpossible killer defects are re-located using saved defect location dataand re-imaged using the e-beam column array's highest resolution 1510.Defects are reviewed and classified using the data resulting from thestep 1510 high-resolution scan 1512.

FIG. 16 shows an example process for improving critical dimension (CD)and overlay metrology. A wafer is prepared with high-order Hadamardtargets 402 written thereon 1300; except that, at step 1306, high-orderHadamard targets 402 are written with critical dimension (CD) controlmarks and (or and/or) overlay marks embedded therein 1602. The resultingcomposite high-order Hadamard targets can be imaged and analyzed toimprove CD and overlay metrology 1604. The substrate is loaded into anEBI tool, and the composite high-order Hadamard targets, and the CD andoverlay marks within particular blocks 302 of the high-order Hadamardtargets 402, are located using design layout database correlation 1606.The CD and overlay marks are imaged 1608, and the resulting image datais correlated (pattern recognition is performed) with (preferably)computer generated templates or (less preferred) reference images.Inspection data from this imaging and analysis is fed back to the designlayout database and/or patterning tool(s) 1610 e.g., for use in makingdesign modifications and tool parameter modifications, and to helpdesignate care areas for higher-resolution inspection, to improve yield.

As shown, a multi-column e-beam inspection system can be configured as amassively parallel CD, overlay, and defect control solution to improveboth parametric and functional yield.

FIG. 17A schematically shows an example of nested Hadamard targets 1700.(In FIGS. 17A, 17B, 18A, 18B and 18C, borders are included solely toclearly delineate Hadamard target blocks 302.) In some embodiments, asshown in FIG. 17A, nested Hadamard targets 1700 can be sized to fitwithin a single scan field 604. Alternatively, nested Hadamard targets1700 can span a larger area, up to an entire wafer 200. Nested Hadamardtargets 1700 can also be regularly or irregularly scattered acrosswafers 200 (e.g., production wafers). A nested Hadamard target 1700comprises a (relatively) larger outer Hadamard target 402 with one ormore smaller Hadamard targets 402 (optionally, recursively) within thelarger target 402. Scan fields containing nested Hadamard targets 1700can be located, for example, between dies or between reticle fields.

FIG. 17B schematically shows an example of nested Hadamard targets 1700.This is an example of a triply nested Hadamard target—a small Hadamardtarget 402 centered in a second Hadamard target 402 which in turn iscentered in the symmetric central block 316 of a third Hadamard target402 (only the symmetric central block 316 of the outermost target isshown here due to scale issues). This also comprises an example of anoverlay mark embedded in a symmetric Hadamard target block 302.

Hadamard targets 402 are easily nested in symmetric central blocks 316(or other blocks) to a number of levels limited by the resolution limitsof the patterning tool. This allows precision and accuracy to beincreased arbitrarily to the physical limits of the tool.

FIGS. 18A, 18B and 18C schematically show examples of conventionaloverlay marks nested in symmetric Hadamard target blocks 302. Box-in-box1802, bar-in-bar 1804 and grating targets 1806 are embeddable inHadamard target blocks 302 (e.g., in a central 316 and/or symmetricHadamard target block 302), and can be used for overlay control. Thesymmetric Hadamard block 302 provides excellent protection fromoptical-proximity and etch-loading effects for these “nested” targets.

FIG. 19 shows an example process flow for e-beam patterning andinspection. Optical lithography 1902 is followed by CEBL 1904 based on aDFY “cut” database—line cuts specified by the design layout database arepatterned on the wafer 200. After development EBI 1906 (ADI, or afterdevelopment inspection, using complementary EBI, or CEBI) is followed bya resist etch step 1908 and then by after etch EBI 1910 (AEI, or afteretch inspection, using CEBI). ADI and AEI can both be accomplished bycomparing images of dies 208 to contents of the design layout database.Results of alignment and/or registration or other imaging of Hadamardtargets 402 with or without embedded or nested overlay or other marks,or of imaging of high-order Hadamard targets 402 with or withoutembedded CD or overlay or other marks, can be fed backwards or forwardsbetween (or among) the design layout database and the CEBL, ADI, etchand AEI processes, to enable design layout and/or beam parameter and/oretch parameter modification to stochastically improve patterning andinspection performance and yield rate.

FIG. 20A schematically shows an example of Hadamard target blocks 302written locally to features comprising or used to write electronicallyfunctional portions of a substrate-borne device (“production features”).(A line-and-cut pattern 2000 is used to illustrate.) As used herein,features “used to write” electronically functional portions of asubstrate-borne device are defined as features which act as boundarieson which or between which electronically functional features areconstructed.

As shown in FIG. 20A, one or more Hadamard target blocks 302—blocks 302(3,0) and (0,2) produced using a Hadamard pattern 300 as shown in FIG.3—are written into what would otherwise be substrate pattern open areas(typically, though not necessarily, areas that will not later be writtenwith production features). Further, these blocks 302 are written beforethe surrounding pattern (e.g., lines and cuts), to serve asre-registration targets for accurate patterning of features, e.g.,features used to write circuits. (The signs (+/−) of the sub-blocks 308in block 302 (0,2) are switched, which preserves edges within the block302 and does not affect the binary correlation (zero) between the blocks302). These Hadamard target blocks 302 can be described as being“embedded” within the surrounding pattern.

Individual (or groups of) Hadamard target blocks 302 (or a completeHadamard target 402) can be used to perform re-registration duringwriting and/or imaging. Beams 204 can image Hadamard blocks 302, andcalculate updated offset information similarly to calculating a newoffset, but using the offset used to image the blocks 302 in addition toimaging results (and other information, e.g., the position of thestage).

Targeting of charged particle beams 204 generally loses accuracy overtime after registration or re-registration. Once a beam 204 has beenregistered with a Hadamard target 402 during a writing and/or imagingpass, re-registration to address targeting errors accumulating duringthe pass can be performed using individual or small arrays of Hadamardtarget blocks 302 (or by a mix of such blocks 302 and/or small arrays ofblocks 302 and/or Hadamard targets 402).

By writing Hadamard target blocks 302 highly locally to areas in whichproduction features will be written—preferably adjacent to andsurrounded by said production features—those blocks 302 can be used forre-registration of charged particle beams 204 used for writing and/orimaging with minimal latency between re-registration and writing and/orimaging. It takes time to deflect a beam to and from a (re-)registrationtarget. Embedding Hadamard target blocks 302 into areas where productionfeatures will be written can help minimize deflection time betweenproduction features and Hadamard target blocks 302 used forre-registration, improving beam 204 accuracy and/or reducing requiredfrequency of re-registration. (In some embodiments, more densely spacingembedded Hadamard target blocks 302 allows more frequentre-registration, further improving accuracy.) This results in reducedpattern overlay and increased yield rate.

FIG. 20B schematically shows an example of Hadamard target blocks 302written locally to features comprising or used to pattern electronicallyfunctional portions of a substrate-borne device. Hadamard target blocks302 can be written using deposition or etch processes; and Hadamardtarget block 302 features written using etch or deposition can bewritten-over by electronically functional features (or other productionfeatures) written using deposition or etch. Hadamard target blocks 302written adjacent to and surrounded by production features can be usedfor highly local re-registration of charged particle beams 204 forpatterning and/or imaging. This increases beam accuracy, resulting inreduced pattern overlay error and increased yield rate.

FIG. 20C schematically shows an example of Hadamard target blocks 302written such that one or more sub-blocks 308 of said blocks 302 willcomprise or be used to pattern electronically functional portions of asubstrate-borne device. In some embodiments, such as the example in FIG.20D (and potentially FIG. 20C, if highlighted lines to be used as partof a Hadamard block extend past the left side of the image), a match inonly one direction between Hadamard sub-block 308 feature sizes andproduction features—allowing use of the target block 302 for thatdirection (x or y) of information—is sufficient. Portions of Hadamardtarget blocks 302 integrated into production features are not merelylocal to, but are part of, features to be patterned, and make efficientuse of substrate surface area. This enables re-registration (and/oralignment or other process metrics) highly local to charged particlebeam patterning and/or imaging, resulting in reduced pattern overlayerror and increased yield rate.

FIG. 20D schematically shows an example of a designated portion 2002 ofpattern comprising or used to write electronically functional features,wherein that portion 2002 is designated for use as a Hadamard targetblock 302. (A region containing function features written to a substrate2004 is shown for illustration.) As shown in FIG. 20D, a designatedportion 2002 of pattern written to a substrate that matches dimensionsof a Hadamard target block 302 and its sub-blocks 308 (scaled to thepattern as written and imaged, or scaled to the pattern as specified inthe design layout database) can be designated for use as a Hadamardtarget block 302 in re-registration. Preferably, search for patternportions matching Hadamard target blocks 302 is performed usingautomated pattern matching of Hadamard target blocks 302 and constituentsub-blocks 308 to the design layout database or to imaged patternwritten to the substrate. Use as Hadamard target blocks 302 of portionsof pattern 2002 that are thus “found” within the design layout databaseor substrate imaging, where those designated portions 2002 comprise orare used to write production features, enables hyper-localre-registration of beams 204. Increased locality of beam 204re-registration to charged particle beam patterning and/or imagingimproves accuracy when patterning and/or imaging the substrate, reducespattern overlay and increases yield rate.

FIG. 21A shows an example process for writing and/or imaging asubstrate. Hadamard target blocks 302 are written adjacent to andsurrounded by locations where the design layout database specifiesproduction features will be written 2102. Alternatively, or in addition,Hadamard target blocks 302 are written so that sub-blocks 308 of saidblocks 302 are written in locations where the design layout databasespecifies production features will be written 2104. (In someembodiments, these sub-blocks 308 are written as the respectiveco-located production features.) Hadamard target blocks 302 are imaged2106 and new offsets for columns are calculated using Hadamard targetblock 302 image data, stage position information and old offsets 2108.Charged particle beams then (continue to) write and/or image productionfeatures using new offsets 2110.

Old offsets can come from, e.g., the design layout database,registration using Hadamard targets 402, or re-registration usingembedded Hadamard target blocks 302. Preferably, registrationinformation from these sources accumulates within repeatedly updatedoffsets as registration and re-registration are repeatedly performed onlocally available Hadamard targets 402 and/or target blocks 302 during acharged particle beam substrate processing pass to maintain locality ofregistration information. This process is preferably frequently repeatedduring charged particle beam substrate processing, e.g., from step 2106during processing of a pattern layer, or from steps 2102 and/or 2104when preparing to process or when initially writing a new pattern layer.This reduces accumulated beam drift and improves beam accuracy, reducingpattern overlay and increasing yield rate.

FIG. 21B shows an example process for writing and/or imaging asubstrate. A pattern matching comparison is performed between Hadamardtarget blocks 302 and production features as specified in the designlayout database to locate production features that could be used(dual-purposed) as Hadamard target blocks 302 in step 2112. Preferably,x and y rescaling of Hadamard target blocks 302 is permitted duringpattern matching to better enable matching. Matching features (Hadamardtarget blocks 302) are then written to the substrate 2114, e.g., priorto or as part of writing a pattern layer. Written matching features canbe used to perform re-registration and other processes related toHadamard targets while writing and/or imaging corresponding patternlayers or (if resistless charged particle beam patterning processes areused) during writing and/or imaging of later pattern layers. Matchingfeatures are imaged and new offsets for columns are calculated usingmatching feature (Hadamard target block 302) image data, stage positioninformation and old offsets 2116. Charged particle beams then (continueto) write and/or image production features using new offsets 2118. Thisprocess is preferably frequently repeated during charged particle beamsubstrate processing, e.g., from step 2116 during processing of apattern layer, or from step 2114 when preparing to process or wheninitially writing a new pattern layer.

According to some but not necessarily all embodiments, there isprovided: A method of substrate lithography and/or inspection usingcharged particle beam columns, comprising the actions of: a) writingmultiple Hadamard targets onto the substrate using multiple firstcharged particle beams; b) imaging said Hadamard targets using multiplesecond charged particle beams; c) calculating offsets for respectiveones of said second beams in at least partial dependence on saidimaging; and d) writing and/or imaging multiple cut features using saidsecond beams, said features being targeted in at least partialdependence on said offsets, wherein individual ones of said beams areprojected by individual ones of the columns, and different ones of thecolumns have different writing areas.

According to some but not necessarily all embodiments, there isprovided: A method of substrate lithography and/or inspection usingcharged particle beam columns, comprising the actions of: a) writingmultiple edge Hadamard targets and multiple inner Hadamard targets ontothe substrate using multiple first charged particle beams; b) firstimaging said edge and inner Hadamard targets using said first beams; c)adding a resist layer to the substrate such that imaging said innerHadamard targets is prevented and imaging said edge Hadamard targets isenabled; d) second imaging said edge Hadamard targets using multiplesecond charged particle beams; e) calculating offsets for respectiveones of said second beams in at least partial dependence on said firstimaging and said second imaging; and f) writing and/or imaging multiplecut features on the substrate using said second beams, said featuresbeing targeted in at least partial dependence on said offsets, whereinindividual ones of said beams are projected by individual ones of thecolumns, and different ones of the columns have different writing areas.

According to some but not necessarily all embodiments, there isprovided: A method of substrate lithography and/or inspection usingmultiple charged particle beam columns, comprising the actions of: a)writing multiple edge targets and multiple inner targets onto thesubstrate using multiple first charged particle beams; b) first imagingsaid edge and inner targets using respective ones of said first beams;c) adding a resist layer to the substrate such that imaging said innertargets is prevented and imaging said edge targets is enabled; d) secondimaging said edge targets using multiple second charged particle beams;e) calculating offsets for respective ones of said second beams in atleast partial dependence on said first imaging and said second imaging;and f) writing and/or imaging multiple cut features on the substrateusing said second beams, said features being targeted in at leastpartial dependence on said offsets, wherein individual ones of saidbeams are projected by individual ones of the columns, and differentones of the columns have different writing areas.

According to some but not necessarily all embodiments, there isprovided: A method of substrate inspection using multiple chargedparticle beam columns, comprising: a) writing high-order Hadamardtargets to the substrate using multiple first charged particle beams; b)imaging multiple features in said high-order Hadamard targets usingmultiple second charged particle beams; c) measuring beam performance inat least partial dependence on said imaging, and determining which ofsaid features were correctly imaged in step b); d) until one or morefeatures of a threshold size are correctly imaged, modifying beamparameters of said second beams in at least partial dependence on saidmeasuring to stochastically improve beam performance, and repeatingsteps b) and c), targeting one or more features in said repeated step b)that are smaller than those previously determined as correctly imaged;and e) imaging multiple cut features on the substrate using said secondbeams with said modified beam parameters, wherein individual ones ofsaid beams are projected by individual ones of the columns, anddifferent ones of the columns have different writing areas.

According to some but not necessarily all embodiments, there isprovided: A substrate lithography and inspection tool, comprising: asubstrate stage; multiple charged particle beam columns, individual onesof said columns configured to produce an individual charged particlebeam, different ones of said columns having different writing areas; andone or more column controllers storing instructions in acomputer-readable non-transitory medium that, when executed, direct saidbeam controllers to: control said columns to write multiple Hadamardtargets onto the substrate; image said Hadamard targets; calculateoffsets for said columns in at least partial dependence on said imageaction; and control said columns to write and/or image multiple cutfeatures, said features being targeted in at least partial dependence onsaid offsets.

According to some but not necessarily all embodiments, there isprovided: A substrate lithography and inspection tool, comprising: asubstrate stage; multiple charged particle beam columns, individual onesof said columns configured to produce an individual charged particlebeam, different ones of said columns having different writing areas; andone or more column controllers storing instructions in acomputer-readable non-transitory medium that, when executed, direct saidbeam controllers to: control said columns to write multiple edgeHadamard targets and multiple inner Hadamard targets in multiple writingareas on the substrate; control said columns to first image said edgeand inner Hadamard targets; control said columns to second image saidedge Hadamard targets using; and calculate offsets for respective onesof said columns in at least partial dependence on said first imageaction and said second image action; and control said columns to writeand/or image multiple cut features on the substrate, said features beingtargeted in at least partial dependence on said offsets.

According to some but not necessarily all embodiments, there isprovided: A substrate lithography and inspection tool, comprising: asubstrate stage; multiple charged particle beam columns, individual onesof said columns configured to produce an individual charged particlebeam, different ones of said columns having different writing areas; andone or more column controllers storing instructions in acomputer-readable non-transitory medium that, when executed, direct saidbeam controllers to: control said columns to write multiple edge targetsand multiple inner targets in multiple writing areas on the substrate;control said columns to first image said edge and inner targets; controlsaid columns to second image said edge targets; calculate offsets forrespective ones of said columns in at least partial dependence on saidfirst image action and said second image action; and control saidcolumns to write and/or image multiple cut features on the substratesaid features being targeted in at least partial dependence on saidoffsets.

According to some but not necessarily all embodiments, there isprovided: A substrate lithography and inspection tool, comprising: asubstrate stage; multiple charged particle beam columns, individual onesof said columns configured to produce an individual charged particlebeam, different ones of said columns having different writing areas; andone or more column controllers storing instructions in acomputer-readable non-transitory medium that, when executed, direct saidbeam controllers to: control said columns to write multiple high-orderHadamard targets in multiple writing areas on the substrate; controlsaid columns to image multiple features in said high-order Hadamardtargets; measure performance in at least partial dependence on saidimaging, and determine which of said features were correctly imaged;until one or more features of a threshold size are correctly imaged,modify beam parameters of said columns in at least partial dependence onsaid measuring to stochastically improve beam performance, andcontrolling said columns to repeat said image multiple target featuresaction, said measure action and said determine action, targeting one ormore features in said repeated image action that are smaller than thosepreviously determined as correctly imaged; and controlling said columnsto image multiple cut features on the substrate using said columns withsaid modified beam parameters.

According to some but not necessarily all embodiments, there isprovided: A method of substrate patterning and/or inspection using oneor more charged particle beam columns, comprising the actions of: a)writing multiple block-based Hadamard targets onto the substrate usingone or more first charged particle beams; b) imaging said Hadamardtargets using one or more second charged particle beams; c) calculatingoffsets for respective ones of said second beams in at least partialdependence on said imaging; and d) writing and/or imaging multiplefeatures using said second beams, said features being targeted in atleast partial dependence on said offsets, wherein individual ones ofsaid beams are projected by individual ones of the columns, anddifferent ones of the columns have different writing areas.

According to some but not necessarily all embodiments, there isprovided: A method of substrate patterning and/or inspection using oneor more charged particle beam columns, comprising: a) writing multiplehigh-order block-based Hadamard targets to the substrate using one ormore first charged particle beams; b) imaging multiple features in saidhigh-order Hadamard targets using one or more second charged particlebeams; c) measuring beam performance in at least partial dependence onsaid imaging, and determining which of said features were correctlyimaged in step b); and d) until one or more features of a threshold sizeare correctly imaged, modifying beam parameters of said second beams inat least partial dependence on said measuring to stochastically improvebeam performance, and repeating steps b) and c), targeting one or morefeatures in said repeated step b) that are smaller than those previouslydetermined as correctly imaged; wherein individual ones of said beamsare projected by individual ones of the columns, and different ones ofthe columns have different writing areas.

According to some but not necessarily all embodiments, there isprovided: A substrate patterning and inspection tool, comprising: one ormore charged particle beam columns, individual ones of said columnsconfigured to produce an individual charged particle beam, differentones of said columns having different writing areas; and one or morecolumn controllers storing instructions in a computer-readablenon-transitory medium that, when executed, direct said beam controllersto: control said columns to write multiple block-based Hadamard targetsonto the substrate; image said Hadamard targets; calculate offsets forsaid columns in at least partial dependence on said image action; andcontrol said columns to write and/or image multiple features, saidfeatures being targeted in at least partial dependence on said offsets.

According to some but not necessarily all embodiments, there isprovided: A substrate patterning and inspection tool, comprising: one ormore charged particle beam columns, individual ones of said columnsconfigured to produce an individual charged particle beam, differentones of said columns having different writing areas; and one or morecolumn controllers storing instructions in a computer-readablenon-transitory medium that, when executed, direct said beam controllersto: control said columns to write multiple high-order block-basedHadamard targets in multiple writing areas on the substrate; controlsaid columns to image multiple features in said high-order Hadamardtargets; measure performance in at least partial dependence on saidimaging, and determine which of said features were correctly imaged;until one or more features of a threshold size are correctly imaged,modify beam parameters of said columns in at least partial dependence onsaid measuring to stochastically improve beam performance, andcontrolling said columns to repeat said image multiple target featuresaction, said measure action and said determine action, targeting one ormore features in said repeated image action that are smaller than thosepreviously determined as correctly imaged; and controlling said columnsto image multiple features on the substrate using said columns with saidmodified beam parameters.

According to some but not necessarily all embodiments, there isprovided: A method of substrate patterning and/or inspection using oneor more charged particle beam columns, comprising the actions of: a)writing multiple Hadamard target blocks onto the substrate using one ormore first charged particle beams, ones of said blocks being written:adjacent to and surrounded by locations in which the design layoutdatabase specifies features comprising or used to write electricallyfunctional features to be written, or such that one or more sub-blocksof said blocks are part of said specified features; b) imaging saidHadamard targets using multiple second charged particle beams; c)calculating new offsets for respective ones of said second beams in atleast partial dependence on said imaging and on offsets previouslycalculated for and used for writing and/or imaging by said second beams;and d) writing and/or imaging said specified features using said secondbeams, said second beams being targeted in at least partial dependenceon said new offsets.

According to some but not necessarily all embodiments, there isprovided: A method of substrate patterning and/or inspection using oneor more charged particle beam columns, comprising the actions of: a)pattern matching Hadamard target blocks to design layoutdatabase-specified features comprising or used to write electricallyfunctional features to be written; b) writing said matching featuresusing first charged particle beams; c) imaging said matching featuresusing second charged particle beams; d) calculating new offsets forrespective ones of said second beams in at least partial dependence onsaid imaging and on offsets previously calculated for and used forwriting and/or imaging by said second beams; and e) writing and/orimaging said specified features using said second beams, said secondbeams being targeted in at least partial dependence on said new offsets.

According to some but not necessarily all embodiments, there isprovided: methods, systems and devices for using charged particle beamtools to pattern and inspect a substrate. The inventors have discoveredthat it is highly advantageous to use patterns generated using theHadamard transform as alignment and registration marks (Hadamardtargets) for multiple-column charged particle beam substrate processingand inspection tools. Hadamard targets can be written to a substrateusing charged particle beams performing, for example, resist-basedlithography or resist-less direct processing. High-order Hadamardtargets can also be patterned and imaged to obtain superior columnperformance metrics for applications such as super-rapid beamcalibration DOE, column matching, and column performance tracking.Hadamard target blocks can be written highly locally to electricallyfunctional pattern portions, or integrated into said pattern portions,thereby enabling re-registration local and contemporaneous to writingand improving beam targeting accuracy following re-registration.Superior alignment and registration, and column parameter optimization,allow significant yield gains.

MODIFICATIONS AND VARIATIONS

As will be recognized by those skilled in the art, the innovativeconcepts described in the present application can be modified and variedover a tremendous range of applications, and accordingly the scope ofpatented subject matter is not limited by any of the specific exemplaryteachings given. It is intended to embrace all such alternatives,modifications and variations that fall within the spirit and broad scopeof the appended claims.

Some embodiments are disclosed herein with respect to wafers. Those ofordinary skill in the art of charged particle beam substrate patterningand inspection will understand that other types of substrates can alsobe used.

Some embodiments are disclosed herein using electron beams and electronbeam columns. Those of ordinary skill in the art of charged particlebeam substrate patterning and inspection will understand that theinventions disclosed herein can also be embodied using other types ofcharged particle beams (e.g., ion beams) and charged particle beamcolumns (e.g., ion beam columns).

Some embodiments disclosed herein refer only to one or the other ofregistration and alignment. It will be apparent to one of ordinary skillin the arts of charged particle beam substrate patterning and inspectionthat some or all of such embodiments can be applied to both registrationand alignment.

In some embodiments, a single charged particle beam column can be usedto pattern and/or image Hadamard targets. In some embodiments, multiplecharged particle beam columns, but less than a full array, can be usedto pattern and/or image Hadamard targets.

In some embodiments, charged particle beam patterning and/or inspectioncan be performed using a resist layer. In some embodiments, chargedparticle beam patterning and/or inspection can be performed withoutusing a resist layer. Those of ordinary skill in the art of chargedparticle beam substrate patterning will understand that referencesherein to “lithography” can also be applied to processes that do not usea resist layer.

In some embodiments, edge and/or inner targets can be written usingresistless patterning processes (e.g., direct addition or directsubtraction), and that techniques disclosed hereinabove can then be usedwith resist layers and related patterning and inspection to maplocations of edge targets to projected locations of inner targets usingprevious imaging of edge and inner targets.

In some embodiments, alignment and/or registration targets other thanHadamard targets can be used.

In some embodiments disclosed herein using edge targets and referringspecifically to Hadamard targets, other alignment and/or registrationmark patterns can be used (e.g., checkerboard patterns, gratingpatterns, box-in-box patterns or bar-in-bar patterns) instead ofHadamard targets.

It will be apparent to those of ordinary skill in the art that, withrespect to some portrayals of size 16×16 sequency-ordered Hadamardmatrices, FIG. 3 is further permuted, as follows. For integer i and jsuch that (i mod 4)=(j mod 4)=0, each 4×4 region comprising (row,column) indices in the range (i . . . i+3, j . . . j+3), starting withindex (0, 0), has been rotated counterclockwise by 90 degrees (pi/2radians). This corresponds to rotating individual blockscounterclockwise by 90 degrees.

In some embodiments, different Hadamard targets 402 (or target blocks302) can be oriented differently on a wafer 200—e.g., an entire Hadamardtarget 402 can be rotated with respect to another Hadamard target 402.

In some embodiments, the same intra-block permutations are performed onall blocks 302 in a Hadamard target 402. In some embodiments, differentintra-block permutations are performed on some or all blocks 302 in aHadamard target 402.

In some embodiments, allowable permutations within a block that maintainedges between adjacent cells include sign-change of the entire block302; reflection of the block 302 about the x and/or y axis (replacingthe block 302 with its mirror image); or rotation of the entire block302 around its center by one, two or three quarter-turns (k*pi/2radians, for integer k, 0<k<4).

In some embodiments in which functions and/or algorithms are used togenerate a Hadamard transform that do not result in N² basis vectors ofN² elements, “blocks” are defined as those non-overlapping portionscovering (tiling) the Hadamard target 402 pattern, of size 4×4 orlarger, that result in binary correlation of pairs of blocks being 0.

In some embodiments, blocks in one or more Hadamard targets written to asubstrate are rearranged (transposed) and the resulting Hadamard targets(the blocks of which can be transposed the same way or in differentways, depending on, e.g., application and the level of security and/oruniqueness desired) are used to identify, track, and/or authenticate theresulting individual product unit (e.g., die) or batch of product units.This can be used for, for example, anti-counterfeit measures.

In some embodiments, Hadamard target 402 patterns can be selected sothat Hadamard target 402 portions smaller than blocks 302 are uniquewith respect to other Hadamard target 402 portions of the same size.

In some embodiments, when preparing for write iterations following edgeHadamard target writing, edge-bead removal is performed to removesufficient resist from edge-proximal portions of the wafer tosufficiently expose the edge Hadamard targets for imaging and alignmentand/or registration.

In some embodiments, steps 118 and 120 are performed by an EBI toolafter, e.g., registration/alignment and patterning using an EBL orcombined EBL/EBI tool.

In some embodiments using edge targets, some or all targets are notHadamard targets.

In some embodiments using edge targets, edge targets are written to asubstrate in locations corresponding to all or substantially all columnswith writing areas containing edge-proximal portions of the substrate.

In some embodiments (e.g., when insufficient substrate surface area isavailable for a complete Hadamard target), fewer than all blocks in aHadamard target are written to a substrate. For example, a 2×3 array ofblocks out of a 3×3 array Hadamard target.

In some embodiments, DOE imaging of high-order Hadamard targets isperformed out-of-order with respect to sizes of features being imaged.

In some embodiments, it can be acceptable for no blocks in a high-orderHadamard target to be correctly imaged using initial beam parametervalues, e.g., where multiple other initial beam parameter valuecandidates are available.

In some embodiments, e.g., where correct imaging of one or moreparticular ones of the blocks or features in a high-order Hadamardtarget corresponds to a threshold for adequate beam performance, it canbe acceptable for all blocks in a high-order Hadamard target to becorrectly imageable by a column.

In some embodiments, a threshold feature size of a high-order Hadamardtarget is required to be correctly imaged multiple times before theimaging beam is considered sufficiently accurate for defect inspection.

It will be apparent to those of ordinary skill in the arts of chargedparticle beam patterning and inspection that while embodiments have beendescribed with respect to particular charged particle detection anddeflection parameters, to the extent other such parameters areadjustable, their effects can also be analyzed and their valuesoptimized as disclosed hereinabove.

In some embodiments using Hadamard targets, edge targets are not used.

In some embodiments (e.g., in which not all columns in an array will bewriting and/or imaging patterns), targets are written by less than allcolumns in an array, and/or less than all columns in an array arealigned and/or registered.

In some embodiments, one, some, or all of the columns can have one ormultiple Hadamard targets located within their respective writing and/orinspection areas; within particular stripes; within particular frames;and/or within particular scan fields.

In some embodiments, high-order Hadamard targets can be configured tocontain one or more blocks effectively imageable using default ortypical EBI e-beam parameter settings.

In some embodiments, high-order Hadamard targets can be configured tocontain blocks comprising a range of average and/or minimum featuresizes which can be used to refine patterning and/or inspectionparameters and/or e-beam parameters.

In some embodiments, some or all edge targets and/or some or all innertargets are high-order Hadamard targets, and/or some or all edge targetsand/or some or all inner targets are non-high-order Hadamard targets.

In some embodiments, Hadamard targets are generated using algorithms orfunctions used to compute Hadamard and/or Walsh transform outputs otherthan those given in Equations 1 and 2.

Some embodiments involving parameter optimization use one or more ofmultiple starting conditions, periodic parameter randomization, orhistorical performance comparisons; e.g., to avoid parameter refinementbecoming trapped in local maxima of relevant performance criteria.

In some embodiments, Hadamard targets and/or high-order Hadamard targetsare located between dies and/or between reticle fields.

Additional general background, which helps to show variations andimplementations, may be found in the following publications, all ofwhich are hereby incorporated by reference: Rafael C. Gonzalez andRichard E. Woods, Digital Image Processing, Addison-Wesley, 1992; YoannBlancquaert and Christophe Dezauzier, “Diffraction based overlay andimage based overlay on production flow for advanced technology node.”,Proc. SPIE Vol. 8681, 2013; Yen-Liang Chen, et al., “Reduction ofimage-based ADI-to-AEI overlay inconsistency with improved algorithm”,Proc. SPIE Vol. 8681, 2013; Nuriel Amir, et al., “Multi layer overlaymeasurement recent developments”, Proc. SPIE Vol. 8681, 2013; T. Kato,et al., “Fundamentals of overlay measurement and inspection usingscanning electron-microscope”, Proc. SPIE Vol. 8681, 2013; Charlie Chen,et al., “DCM: device correlated metrology for overlay measurements”,Proc. SPIE Vol. 8681, 2013; Osamu Inoue, et al., “In-die overlaymetrology by using CD-SEM”, Proc. SPIE Vol. 8681, 2013; Cen Shawn Wu, etal., “High-energy electron beam lithography for nanoscale fabrication”,Lithography, INTECH, 2010; U.S. Pat. No. 7,271,907; U.S. Pat. No.6,355,994; U.S. Pat. No. 6,617,587; U.S. Pat. No. 6,734,428; U.S. Pat.No. 6,738,506; U.S. Pat. No. 6,777,675; U.S. Pat. No. 6,844,550; U.S.Pat. No. 6,872,958; U.S. Pat. No. 6,943,351; U.S. Pat. No. 6,977,375;U.S. Pat. No. 7,122,795; U.S. Pat. No. 7,227,142; U.S. Pat. No.7,435,956; U.S. Pat. No. 7,456,402; U.S. Pat. No. 7,462,848; U.S. Pat.No. 7,786,454; U.S. Pat. No. 7,928,404; U.S. Pat. No. 7,941,237; U.S.Pat. No. 8,242,457; and U.S. Pat. No. 8,384,048; U.S. Pat. No.8,999,627; U.S. Pat. No. 8,999,628; U.S. Pat. No. 9,184,027; and U.S.Pat. No. 9,207,539.

Additional general background, which helps to show variations andimplementations, as well as some features which can be implementedsynergistically with the inventions claimed below, may be found in thefollowing US patent applications. All of these applications have atleast some common ownership, copendency, and inventorship with thepresent application, and all of them, as well as any material directlyor indirectly incorporated within them, are hereby incorporated byreference: U.S. patent application Ser. No. 14/522,563; and U.S. patentapplication Ser. No. 15/171,922.

None of the description in the present application should be read asimplying that any particular element, step, or function is an essentialelement which must be included in the claim scope: THE SCOPE OF PATENTEDSUBJECT MATTER IS DEFINED ONLY BY THE ALLOWED CLAIMS. Moreover, none ofthese claims are intended to invoke paragraph six of 35 USC section 112unless the exact words “means for” are followed by a participle.

The claims as filed are intended to be as comprehensive as possible, andNO subject matter is intentionally relinquished, dedicated, orabandoned.

What is claimed is:
 1. A method of substrate patterning and/orinspection using one or more charged particle beam columns, comprisingthe actions of: a) writing multiple block-based Hadamard targets ontothe substrate using one or more first charged particle beams; b) imagingsaid Hadamard targets using one or more second charged particle beams;c) calculating offsets for respective ones of said second beams in atleast partial dependence on said imaging; and d) writing and/or imagingmultiple features using said second beams, said features being targetedin at least partial dependence on said offsets, wherein individual onesof said beams are projected by individual ones of the columns, anddifferent ones of the columns have different writing areas.
 2. Themethod of claim 1, wherein, in step a), said first beams write at leastone Hadamard target in the writing area of each column projecting saidsecond beams.
 3. The method of claim 1, wherein said first beams areproduced by the same charged particle beam tool, and/or by the samearray of columns, and/or by the same columns, as said second beams. 4.The method of claim 1, wherein the substrate is moved from one stage toa different stage between step a) and step b).
 5. The method of claim 1,wherein different ones of said beams perform said writing and/or saidimaging differently and simultaneously.
 6. The method of claim 1,wherein said offsets are calculated also in at least partial dependenceon the design layout database of the substrate and the position of thestage on which the substrate is mounted.
 7. The method of claim 1,wherein said features comprise line-cuts and holes.
 8. The method ofclaim 1, wherein said imaging said Hadamard targets comprisesinitial-imaging expected locations of center and/or most-symmetricblocks of said Hadamard targets at least sufficiently to determine whichportions of said Hadamard targets were imaged, calculating actuallocations of said blocks in at least partial dependence on saidinitial-imaging, and refined-imaging at said actual locations.
 9. Themethod of claim 1, wherein at least some of said Hadamard targets arehigh-order Hadamard targets.
 10. The method of claim 1, wherein saidfirst beams write features to the substrate in addition to said Hadamardtargets.
 11. The method of claim 1, wherein two or more of the blocks inat least one of said Hadamard targets are transposed within saidHadamard target.
 12. The method of claim 11, wherein said Hadamardtargets comprising transposed blocks are used to identify, track, and/orauthenticate the individual substrate-derived product unit to which theyare written.
 13. A method of substrate patterning and/or inspectionusing one or more charged particle beam columns, comprising: a) writingmultiple high-order block-based Hadamard targets to the substrate usingone or more first charged particle beams; b) imaging multiple featuresin said high-order Hadamard targets using one or more second chargedparticle beams; c) measuring beam performance in at least partialdependence on said imaging, and determining which of said features werecorrectly imaged in step b); and d) until one or more features of athreshold size are correctly imaged, modifying beam parameters of saidsecond beams in at least partial dependence on said measuring tostochastically improve beam performance, and repeating steps b) and c),targeting one or more features in said repeated step b) that are smallerthan those previously determined as correctly imaged; wherein individualones of said beams are projected by individual ones of the columns, anddifferent ones of the columns have different writing areas.
 14. Themethod of claim 13, wherein said beam parameters are selected from: beamenergy, beam focus, exposure time, beam current, beam landing energy,beam size, beam initial position, and beam scan rate.
 15. The method ofclaim 13, wherein said measuring uses criteria selected from: beamresolution, contrast, signal-to-noise ratio, edge-sharpness, anddeflection accuracy.
 16. The method of claim 13, wherein the substrateis not removed from the stage between step b) and step e).
 17. Themethod of claim 13, wherein said targets are generated using thediscrete Hadamard and/or Walsh transform basis kernels using N≥10. 18.The method of claim 13, wherein said targets are configured such that,using initial and/or non-optimized beam parameters, at least somefeatures of said targets can be correctly imaged and at least sometarget features cannot be correctly imaged.
 19. The method of claim 13,wherein steps b) through d) are repeated multiple times, on one or moredifferent substrates, using multiple different high-order Hadamardtargets comprising either or both of (1) a high-order Hadamard targetwith transposed blocks, or (2) multiple different Hadamard and/or Walshtransform-derived patterns.
 20. The method of claim 13, wherein if,within a specified number of iterations of step d) or a specified amountof time, said measured beam performance of a particular one of saidsecond beams fails to reach a pass threshold or decreases significantlywith respect to prior measured beam performance, or said particularsecond beam fails to correctly image features of said threshold size,then the corresponding column is inspected for defects and/or repairedand/or replaced.
 21. The method of claim 13, wherein steps b) through d)are repeated until the rate of improvement in measured beam performanceand/or the rate of decrease in correctly imaged feature size falls belowa threshold rate.
 22. The method of claim 13, wherein two or more of theblocks in at least one of said Hadamard targets are transposed withinsaid Hadamard target.
 23. A substrate patterning and inspection tool,comprising: one or more charged particle beam columns, individual onesof said columns configured to produce an individual charged particlebeam, different ones of said columns having different writing areas; andone or more column controllers storing instructions in acomputer-readable non-transitory medium that, when executed, direct saidbeam controllers to: control said columns to write multiple block-basedHadamard targets onto the substrate; image said Hadamard targets;calculate offsets for said columns in at least partial dependence onsaid image action; and control said columns to write and/or imagemultiple features, said features being targeted in at least partialdependence on said offsets.
 24. The tool of claim 23, wherein saidcolumn controllers are configured to control said columns to write atleast one Hadamard target in the writing area of each column performingsaid write and/or image multiple features action.
 25. The tool of claim23, wherein said column controllers are configured to control differentones of said columns to perform said write actions and said imageactions differently and simultaneously.
 26. The tool of claim 23,further comprising a substrate stage on which the substrate is mounted,wherein said column controllers are configured to calculate said offsetsalso in at least partial dependence on the design layout database of thesubstrate and the position of said stage.
 27. The tool of claim 23,wherein said features comprise line-cuts and holes.
 28. The tool ofclaim 23, wherein said image Hadamard targets action comprisesinitial-imaging expected locations of center and/or most-symmetricblocks of said Hadamard targets at least sufficiently to determine whichportions of said Hadamard targets were imaged, calculating actuallocations of said blocks in at least partial dependence on saidinitial-imaging, and refined-imaging at said actual locations.
 29. Thetool of claim 23, wherein at least some of said Hadamard targets arehigh-order Hadamard targets.
 30. A substrate patterning and inspectiontool, comprising: one or more charged particle beam columns, individualones of said columns configured to produce an individual chargedparticle beam, different ones of said columns having different writingareas; and one or more column controllers storing instructions in acomputer-readable non-transitory medium that, when executed, direct saidbeam controllers to: control said columns to write multiple high-orderblock-based Hadamard targets in multiple writing areas on the substrate;control said columns to image multiple features in said high-orderHadamard targets; measure performance in at least partial dependence onsaid imaging, and determine which of said features were correctlyimaged; until one or more features of a threshold size are correctlyimaged, modify beam parameters of said columns in at least partialdependence on said measuring to stochastically improve beam performance,and controlling said columns to repeat said image multiple targetfeatures action, said measure action and said determine action,targeting one or more features in said repeated image action that aresmaller than those previously determined as correctly imaged; andcontrolling said columns to image multiple features on the substrateusing said columns with said modified beam parameters.
 31. The tool ofclaim 30, wherein said beam parameters are selected from: beam energy,beam focus, exposure time, beam current, beam landing energy, beam size,beam initial position, and beam scan rate.
 32. The tool of claim 30,wherein said measuring uses criteria selected from: beam resolution,contrast, signal-to-noise ratio, edge-sharpness, and deflectionaccuracy.
 33. The tool of claim 30, wherein said targets are generatedusing the discrete Hadamard and/or Walsh transform basis kernels usingN≥10.
 34. The tool of claim 30, wherein said targets are configured suchthat, using initial and/or non-optimized beam parameters, at least somefeatures of said targets can be correctly imaged and at least sometarget features cannot be correctly imaged.
 35. The tool of claim 30,wherein said image multiple target features action, said measure anddetermine actions, and said modify and repeat actions are repeatedmultiple times on one or more different substrates, prior to saidimaging features action, using multiple different high-order Hadamardtargets comprising either or both of (1) a high-order Hadamard targetwith transposed blocks, or (2) multiple different Hadamard and/or Walshtransform-derived patterns.
 36. The tool of claim 30, wherein if, withina specified number of iterations of said modify and repeat actions or aspecified amount of time, said measured beam performance of a particularone of said columns fails to reach a pass threshold or decreasessignificantly with respect to prior measured beam performance, or saidparticular column fails to correctly image features of said thresholdsize, then said particular column is inspected for defects and/orrepaired and/or replaced.
 37. The tool of claim 30, wherein said imagemultiple target features action, said measure and determine actions, andsaid modify and repeat actions are repeated until the rate ofimprovement in measured beam performance and/or the rate of decrease incorrectly imaged feature size falls below a threshold rate.